Migrating from 0.3 to 0.4

NuSA 0.4 intentionally changes how solved state is represented. The central change is simple:

NuSA 0.3: solve and read mutable state from Model / Node / Element
NuSA 0.4: solve and read a stable StaticResult snapshot

The migration is therefore mostly a matter of keeping the object returned by solve() and reading solved quantities from that result.

Keep the solve result

0.3-style code often ignored the return value:

model.solve()

In 0.4, keep it explicitly:

result = model.solve()

Node displacements

0.3:

model.solve()
print(node.ux)
print(node.uy)

0.4:

result = model.solve()
displacement = result.displacement(node)
print(displacement["ux"])
print(displacement["uy"])

Node no longer stores solved displacement attributes.

Nodal forces and reactions

0.3 code could read force-like values from mutable nodes or model state.

0.4 distinguishes applied loads, generalized nodal forces, and reactions:

result.applied_load(node)
result.nodal_force(node)
result.reaction(node)

Use reaction(node) for support reactions.

Element results

0.3:

print(element.sx)
print(element.fx)

0.4:

values = result.element_result(element)
print(values["axial_stress"])
print(values["axial_force"])

Canonical result names depend on the element family. See Results and Elements for the complete schemas.

Reports

0.3:

model.simple_report()

0.4:

result = model.solve()
result.simple_report()

Reports consume the solved snapshot rather than mutable model state.

Visualization

Problem visualization and solved visualization are now separated.

0.3-style solved plotting:

model.plot_deformed_shape()
model.plot_nodal_result("sxx")

0.4:

from nusa import plot_model

plot_model(model)                       # problem definition

result = model.solve()
result.plot_deformed_shape()            # solved geometry
result.plot_nodal_field("stress_xx")   # solved field

Beam diagrams likewise move to the result:

result.plot_shear_diagram()
result.plot_moment_diagram()

Global stiffness matrix and assembly state

The following 0.3-style public solved/assembly interfaces are no longer part of the 0.4 public API:

model.assemble()
model.stiffness_matrix
model.displacements
model.nodal_forces
model.reactions

Assembly and reduced-system state are implementation details of the analysis. The public solved interface is StaticResult.

Module layout

The old catch-all nusa.core module has been removed.

Use the top-level public imports when possible:

from nusa import Node, Element, Model

The underlying modules are now:

nusa.node      -> Node
nusa.element   -> Element and concrete elements
nusa.model     -> Model and concrete model families

Typical before/after example

0.3:

model.solve()

print(node.ux)
print(model.reaction(node))
model.simple_report()
model.plot_deformed_shape()

0.4:

result = model.solve()

print(result.displacement(node)["ux"])
print(result.reaction(node))
result.simple_report()
result.plot_deformed_shape()

Summary table

Common 0.3 to 0.4 replacements

0.3 pattern	0.4 replacement
node.ux, node.uy, …	result.displacement(node)
node/model solved forces	result.nodal_force(node) or result.reaction(node)
element.sx, element.fx, …	result.element_result(element)
model.simple_report()	result.simple_report()
model.plot_deformed_shape()	result.plot_deformed_shape()
model.plot_nodal_result(...)	result.plot_nodal_field(...)
model.plot_element_result(...)	result.plot_element_field(...)
model.assemble()	internal analysis operation; no direct public replacement
model.stiffness_matrix	internal analysis data; no direct public replacement
nusa.core	nusa.node, nusa.element, nusa.model or top-level imports

For new code, start with Getting started and use How NuSA works as the conceptual reference for ownership of problem and solution state.